When to plant · 38 cities · zones 5b–6a

When to plant basil in Illinois

Start Genovese Basil seeds indoors around Mar 20 and transplant around May 1 — the Illinois statewide median, counted from a last spring frost of Apr 17 across 1,402 ZIP codes and 192 NOAA stations.

Mar 20Start indoors4 weeks before last frost
May 1Plant outApr 21 – May 11 across the state
Apr 17Last spring frostmedian · 1 in 10 years after May 3
Jun 30First harvest60 days from transplant

The rule: Basil is damaged below about 50 °F, well before frost: transplant two weeks after the last frost, not on it.

Illinois basil, by step

Statewide median last frost Apr 17, first fall frost Oct 21, 2027 season. Each cultivar's own indoor lead time and days to maturity, same engine as the Plan Builder.

CultivarStart indoorsPlant outFirst harvestDays
Genovese BasilGenoveseMar 20May 1Jun 3060 from transplant

Tight means first harvest lands within two weeks of the median first fall frost. Statewide dates are the ZIP-weighted median of every NOAA 1991–2020 station Illinois's ZIP codes resolve to.

Basil in Illinois, city by city

Genovese Basil, scheduled from each city's nearest NOAA station — the same dates as its frost page.

CityLast frostStart indoorsPlant outFirst harvest
Chicagozone 6aApr 10Mar 13Apr 24Jun 23
Aurorazone 5bApr 19Mar 22May 3Jul 2
Napervillezone 5bApr 28Mar 31May 12Jul 11
Jolietzone 5bApr 19Mar 22May 3Jul 2
Rockfordzone 5bApr 24Mar 27May 8Jul 7
Elginzone 5bApr 26Mar 29May 10Jul 9
Springfieldzone 6aApr 15Mar 18Apr 29Jun 28
Peoriazone 6aApr 16Mar 19Apr 30Jun 29
Champaignzone 6aApr 15Mar 18Apr 29Jun 28
Waukeganzone 6aApr 30Apr 2May 14Jul 13
Cicerozone 6aApr 11Mar 14Apr 25Jun 24
Bloomingtonzone 6aApr 21Mar 24May 5Jul 4
Schaumburgzone 5bApr 30Apr 2May 14Jul 13
Evanstonzone 6aApr 26Mar 29May 10Jul 9
Arlington Heightszone 6aApr 19Mar 22May 3Jul 2
Bolingbrookzone 6aApr 20Mar 23May 4Jul 3
Decaturzone 6aApr 14Mar 17Apr 28Jun 27
Palatinezone 5bApr 25Mar 28May 9Jul 8
Skokiezone 6aApr 26Mar 29May 10Jul 9
Des Plaineszone 6aApr 16Mar 19Apr 30Jun 29
Orland Parkzone 6aApr 20Mar 23May 4Jul 3
Oak Lawnzone 6aApr 10Mar 13Apr 24Jun 23
Mount Prospectzone 6aApr 19Mar 22May 3Jul 2
Berwynzone 6aApr 11Mar 14Apr 25Jun 24
Tinley Parkzone 6aApr 23Mar 26May 7Jul 6
Wheatonzone 5bApr 28Mar 31May 12Jul 11
Normalzone 6aApr 25Mar 28May 9Jul 8
Oak Parkzone 6aApr 11Mar 14Apr 25Jun 24
Hoffman Estateszone 5bApr 30Apr 2May 14Jul 13
Downers Grovezone 6aApr 28Mar 31May 12Jul 11
Plainfieldzone 5bApr 20Mar 23May 4Jul 3
Glenviewzone 6aApr 19Mar 22May 3Jul 2
Elmhurstzone 6aApr 16Mar 19Apr 30Jun 29
Lombardzone 6aApr 28Mar 31May 12Jul 11
Buffalo Grovezone 6aApr 19Mar 22May 3Jul 2
Molinezone 5bApr 24Mar 27May 8Jul 7
Crystal Lakezone 5bMay 1Apr 3May 15Jul 14
Romeovillezone 6aApr 20Mar 23May 4Jul 3

What Illinois basil need

SeedsThe cultivar decides the sauce. Everything downstream is damage control.
  • Genovese Sweet Basil Seed

    The large-leaf, low-anise Italian basil that pesto is defined by. Thai and lemon basils are good plants and wrong ingredients.

StartSoil temperature and light intensity, indoors, weeks before your frost date.
  • Organic Seed Starter Potting MixMust have

    Seed-starting mix is not potting soil with a nicer label — it is finer, lighter, and low in nutrients on purpose, because a seedling's first roots want air and moisture, not fertiliser.

  • T8 Full-Spectrum Grow Lights, 1 ft 4-packMust have

    A south window in March delivers a fraction of the light a pepper seedling needs, and the plant tells you by stretching. Two inches of LED above the canopy for 16 hours a day fixes it permanently.

GrowRoot volume, nutrition and structure. Where most home crops actually fail.
  • 5-Gallon Fabric Grow Bags, 5-Pack

    Fabric pots air-prune roots and drain faster than a plastic pot can, which is the entire reason container tomatoes fail. Five gallons is the honest minimum for a pepper; a tomato wants ten.

  • Ocean Forest Potting SoilMust have

    Pre-charged with enough nutrition to carry a transplant for its first month without feeding, which is exactly the window when most container plants stall.

HarvestTiming, handling, and weighing what you actually got.
  • 6" Micro-Tip Pruning SnipsMust have

    Ninety percent of sauce-garden cutting is snipping a pepper stem or a basil node, and a fine-tipped snip does it better than any pruner. Pulling peppers by hand tears the branch.

CookReduction, texture, and the non-reactive pans that keep tomato tasting like tomato.
  • Mesh Strainers, Stainless, 3-Count

    The last pass before bottling. A fine mesh catches the skin fragments and seed shards that make a hot sauce gritty and clog a woozy bottle's dripper insert.

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Basil in Illinois: questions

When should I plant basil in Illinois?

Transplant around May 1 at the statewide median; across the state that date runs from Apr 21 in the warmest tenth of Illinois's ZIP codes to May 11 in the coldest. To cut the freeze risk to one year in ten, count from May 3 instead of the median last frost. Use the city table for your own town.

When do I start basil seeds indoors in Illinois?

Around Mar 20 for Genovese Basil: 4 weeks before the statewide median last frost, on soil held at 70–80 °F.

When is the last frost in Illinois?

The ZIP-weighted median of NOAA 1991–2020 station medians is Apr 17. In the warmest tenth of Illinois's ZIP codes the median last frost falls on or before Apr 7; in the coldest tenth, on or after Apr 27.

When will Illinois basil be ready to harvest?

Genovese Basil planted on the statewide date is ready around Jun 30: 60 days from transplant.

More for Illinois

Basil in every state → · Illinois frost dates → · How frost-date math works →